A number of inertia latch mechanisms have been devised for preventing forward tilting of the front seat back rest under sudden deceleration conditions, such as incident to front end collisions, while permitting such forward tilting to accommodate rear passenger ingress and egress without the inconvenience of actuating a manual release mechanism. Examples of known prior inertia latch constructions include the following issued U.S. Pat. Nos. 2,873,794, 4,082,353, 4,103,967, 3,674,309, 4,010,979 and 4,118,067. Another known prior inertia latch mechanism is disclosed in co-pending U.S. Application Ser. No. 931,306 filed by Wolfgang Osterhold.
Various problems and limitations have been encountered in prior constructions which the present improvement is directed to overcome. For example, with prior constructions undesired disabling of the inertia latch may occur when packages loaded in the back seat compartment press against and displace seat back slightly from full back position to a point where inertia incident to sudden deceleration would be inoperative to engage the latch; when the inertia element is mounted on the seat back hinge member, sudden forward tilting movement of the seat back, as by a rear seat passenger bracing himself in anticipation of an accident, may disable the inertia element from operating effectively upon impact deceleration; likewise even when the inertia element is mounted on the seat hinge member, if it is provided with a normally open or unlatched condition which requires deceleration inertia to move it into a latched position, a rapid forward tilting movement as caused by bracing of a rear seat passenger anticipating an accident may disable the inertia latch before impact deceleration has an opportunity to effectively actuate the latch mechanism. Furthermore, if the latch is not actuated by each forward tilting movement of the seat back and is only actuated by inertia upon sudden deceleration, friction build-up by dirt accumulation or otherwise may prevent or delay actuation when needed.